In U.S. Pat. No. 6,837,892, for “Miniature Bone-attached Surgical Robot” to one of the inventors of the present application, for there is described a miniature surgical robot attached directly to a bone of a patient, the robot's position being registered relative to preoperative images taken of the operation site. Because of the rigid attachment of the robot to the patient's bone structure, the position of the robot is fixed relative to the bone or bones to be operated on, such that motion of the patient during the operation, whether from the breathing of the patient, or whether from actual movement of the patient's body position, does not affect the position of the operating tool held by the robot relative to the bone or bones to be operated on.
In U.S. Pat. No. 7,887,567 for “Apparatus for Spinal Fixation of Vertebrae”, having a common inventor with the present application, there is described an apparatus for use of surgical robot in performing orthopedic operations on the spine, using a framed device in the form of a bridge for fixing a number of vertebrae together into positions which are uniquely defined relative to the bridge, but which can move relative to the external environment. The fixation generated by such a bridge is especially useful in Computer Assisted Surgery procedures, such as by using a pre-programmed robot mounted on the bridge itself to perform the surgery. Alternative embodiments of the bridge may be used either for performing surgery in one procedure on a number of vertebrae of the spine, or as a reference frame for performing surgery at different locations along the spine, while providing an alignment reference along major lengths of or along all of the spine. These systems are also characterized in that they enable the performance of minimally invasive procedures, with the robot supported by clamps having small cross sections, attached to the bone or bones on which the surgical procedure is being performed.
However, in either of the systems described in the above referenced prior art, if the robot is attached rigidly to the patient's bone, either directly to the bone, or on a structure such as a bridge attached rigidly to the bone, and significant force is exerted by the surgeon onto a surgical tool, such as a surgical drill, there is a danger that the force of the tool on the bone, or the components of side forces on the drill guide transferred to the bone-mounting element, may be sufficient in some cases, to detach the attachment clamp from the bone, such that the robot position is no longer defined relative to the bone. Even if complete detachment does not occur, the exerted force may be sufficient to overcome the clamping friction of the clamp with the bone, and thus to shift the position of the clamp on the bone, with the same end result of loss of positional relationship between the robot and the bone. Furthermore, even if no movement of the clamp from the bone occurs, such excessive force may result in bending of the mechanical attachment member connecting the bone to the robot or the robot support, such that this too would cause the loss of the defined spatial relationship between the robot coordinate system and the bone.
There therefore exists the need for a robotic surgical system that can overcome at least some of the above mentioned disadvantages of prior art systems, such as an ability to withstand high forces exerted on the robot while still maintaining minimally invasive bone clamping techniques.
The disclosures of each of the publications mentioned in this section and in other sections of the specification, are hereby incorporated by reference, each in its entirety.